The most common and most likely answer to this crossword clue is the 9 letter word SHORTSTOP
I've seen this crossword clue in The Times
S
H
O
R
T
S
T
O
P
More clues leading to the result SHORTSTOP
- Fielder, inadequate, returning trophies
- Baseball player’s casual two-piece outfit?
- Position of diamonds in one item of clothing and another
- Fielder's items of clothing
- Two things put on six of diamonds?
- Baseball player‘s casual clothing combination
- Baseball player‘s gear suitable for athletes
- Baseball player’s sports clothes?
- Briefly stay with baseball player
- American player in two garments
Buddy explains!

The straight part
We know that "six of diamonds" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case six of diamonds = shortstop.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SHORTSTOP mean?
SHORTSTOP noun- The infield defensive player that stands between the second baseman and the third baseman.
- A nimble defender.
- A player who is short of money.